Energy cost of walking, symptomatic fatigue and perceived exertion in persons with multiple sclerosis

A higher energy cost of walking (Cw) is sometimes observed in MS, and could contribute to fatigue. The purpose of this study was to compare Cw at three speeds in MS and controls, and determine the effects of walking speed on fatigue and perceived exertion. We hypothesized that MS would have higher Cw, fatigue and exertion during walking than controls. Ten persons with MS and 14 controls of similar age and physical activity levels were studied. Oxygen consumption (VO2) was obtained at rest and during treadmill walking at 0.6 and 1.4ms(-1), and preferred speed. Cw was calculated as net VO2:velocity. Fatigue and exertion were assessed using the visual analog fatigue and modified Borg scales, respectively. Preferred treadmill speed was not different between groups. Cw was higher in MS than controls across walking speeds (p=0.003), with a group-by-speed interaction indicating higher Cw in MS at 0.6ms(-1) (p=0.001), but not at preferred speed or 1.4ms(-1). MS reported greater fatigue (p=0.001) and exertion (p=0.004) at all speeds. Despite similar preferred speeds, and Cw at preferred and fast speeds, MS exhibited higher fatigue and exertion at all walking speeds. These results suggest that increased energy demands in MS are most notable at low speeds such as those used in everyday activities, which may contribute to fatigue over the day.